1. Technical Field
The present invention relates to a positioning system in a communication network of an inter-base station asynchronous system without a common reference timing such as the same clock between communication base stations, a terminal device, a control method of terminal device, a control program of a terminal device, and a computer readable recording medium recording the control program of the terminal device.
2. Related Art
In the past, for example, in a so-called digital mobile communication system in a CDMA (Code Division Multiple Access) system, a method of detecting a position using an arrival time difference of a receiving signal between a plurality of base stations and a mobile wireless terminal devices relying on the assumption that a clock synchronization is assured among the plural base stations was known (for example, JP A-7-181242).
However, in order to establish a system for synchronizing a clock among respective base stations which are numerously located across the country, there is a problem that an economic burden is serious.
Correspondingly, a technology has been proposed, wherein a position management station to manage the mutual time difference information of a plurality of base stations is provided in a communication network of an inter-base station asynchronous system and this position management station measures the position of a mobile terminal (for example, JP A-11-252632).
However, according to the related art technology, the large-scale system change is required in the system to obtain a arrival time difference between a timing signal which has been sent from each base station and a timing signal which is received from other base station and this causes a high economic burden in its establishment.
Further, this involves a problem that the position of the mobile terminal cannot be positioned in the case that the signals cannot be received from three or more base stations.